A rotary fluid compressor provided with a vane, more particularly, a rocking rotor type, is constructed as shown in FIG. 1 where a vane 4 is inserted into a vane groove 3 formed in a rotor housing 2 within a case 1. Vane 4 is freely movable into and removable from vane groove 3. A rotor 5 is mounted rotatably on a crankshaft 6, the latter being concentric with the rotor housing 2. Vane 4 is urged inwardly by a spring, and thus moves back and forth in rotor housing 2 in response to rotation of eccentric rotor 5. In operation, as shown in FIG. 2, vane 4 moves slidably within vane groove 3 with an inclination in the rotation direction of rotor 5 due to frictional pulling by rotor 5. With this construction there arises a problem of abrasion at a vane nose 10, between an inlet portion 9 of vane groove 3 and a side 11 of vane 4, and between a back end portion 12 of vane 4 and a side surface 7 of vane groove 3. Particularly, between vane side 11 and vane groove inlet portion 9 a biting abrasion takes place due to accumulation of abrasive particles in vane groove 3, in addition to sliding abrasion. Therefore, it is necessary to fabricate the vane of the rotary fluid compressor from materials having a superior wear resistance.
The leading materials known to date for compressor. vanes are SUJ2 (a high carbon chrome bearing steel) and SKH9 (a high speed tool steel) specified in the JIS (Japan Industrial Standards). These materials, however, have some drawbacks with respect to their wear resistance. In the case that SUJ2 material is used to form the vane, the amount of precipitation of Cr carbide, which has a high hardness, is so little that its wear resistance is inferior, and thus abrasive wear of the vane itself is high in comparison to the rotor and the vane groove portion which is touches. On the other hand, in the case of SKH9, the precipitation of high hardness carbides including Cr, Mo, W and V is so high that the rotor and the vane groove tend to suffer higher wear than the vane.